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FEBS Lett. 1996 Nov 25;398(1):26-30.

14-3-3 proteins associate with the regulatory phosphorylation site of spinach leaf nitrate reductase in an isoform-specific manner and reduce dephosphorylation of Ser-543 by endogenous protein phosphatases.

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US Department of Agriculture, Agricultural Research Service, Department of Horticulture, North Carolina State University, Raleigh 27695-7631, USA.


Three lines of evidence indicate that the 14-3-3 proteins that inactivate the phosphorylated form of spinach leaf NADH:nitrate reductase (NR) bind to the enzyme at the regulatory phosphorylation site (Ser-543). First, a phosphorylated synthetic peptide based on the regulatory site can prevent and also reverse the inactivation of phospho-NR caused by 14-3-3 proteins. Second, sequence-specific and phosphorylation-dependent binding of the aforementioned synthetic peptide to the 14-3-3 proteins was demonstrated in vitro. Third, 14-3-3 proteins were required for the ATP-dependent phosphorylation of NR (as assessed by activity measurements) in the presence of NR-kinase and leaf protein phosphatases. Lastly, we demonstrate specificity of recombinant Arabidopsis 14-3-3 isoforms in the interaction with phospho-NR: omega> chi> upsilon>>> phi, psi.

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